Permanent fittings are commonly used for connecting metal tubes and pipes to eachother for use in a variety of applications, for example for the conveyance of hydraulic control fluids in the aerospace industry. In this application, the connection between the tubes and fitting must be secure in order to withstand vibrations and adverse conditions.
One type of commonly used fitting is an axially swaged fitting, such as the Rynglok (trademarked product) fittings manufactured by Eaton Corporation. Other axially swaged fittings are available and utilize substantially similar construction and methods to swage the fitting onto a tube. Another example of these axially swaged fittings are the Permalite (trademarked product) brand from Permaswage. These axially swaged fittings utilize a sleeve surrounding the tubes to be joined and one or more swaging ring about the sleeve. The ring and sleeve have complimentary geometry such that as the swaging ring is positioned onto the sleeve, the sleeve collapses the tube to thereby swage the pieces together.
In order to effectuate the swaging process, a lubricant may be placed between the sleeve and swaging ring, thereby allowing the swaging process by reducing friction between the ring and sleeve. This reduces the chance of scarring or gouging the surface of either the ring or sleeve which may cause the swaging ring to lock up and be unable to complete the swaging process, or may damage the ring or sleeve.
The wing of an aircraft requires a number of hydraulic control lines to operate control structure on that portion of the aircraft. These control lines require a significant amount of open space, and may therefore be passed through the fuel storage sections on the wings of the aircraft. There are therefore a large number of fittings adjacent the fuel of the aircraft, and therefore care must be taken to ensure a secure and safe connection.
Electrical events are possible in the hydraulic lines, for example due to system fault or other anomalies in the hydraulic system, and this may cause electrical current to flow along one or more of the tubes. It has previously been assumed that as the electrical current flows from one tube to another through the fitting that the current flows from the first tube, through the sleeve, and then to the second tube, with the swaging rings being outside of the current path. This path of electrical current ensures that current flows cleanly through the fitting without discharges or excess heat buildup.
However, further investigation has revealed that the swaging rings are within the current path, and current travels from the first tube, through the sleeve, to the first swaging ring, back to the sleeve, to the second swaging ring, back to the sleeve, and finally to the second tube. Any lubrication remaining around or between the swaging rings and sleeve may therefore be within the electrical path. Because of the low electrical conductivity of the lubricant, as current flows through the material it acts as a resistor and heats up. This is undesirable for hydraulic lines which run through a fuel storage area, such as on an airplane. Prior art axially swaged fittings do not address this problem, and therefore may be unsuitable for providing a complete conductive path from one tube to another through the swaged fitting. It is therefore a principal object of the present disclosure to provide an axially swaged fitting which provides a complete conductive path through metal components to eliminate the risk of sparking or heat buildup in an axially swaged fitting.
While this problem is identified primarily with respect to aircraft, the apparatus may be used in other applications including, without limitation, watercraft, space vehicles, submarines, automobiles, buildings, industrial hydraulic lines, unmanned vehicles, or any other application. The apparatus may also be used for other, non-hydraulic systems in the same manner as traditional swaged fittings.
Therefore, there is proposed a novel axially swaged fitting which eliminates the problems of the prior art.